While performing the necessary work on private properties referred to in § 13.16.440, the Public Works Director or duly authorized employees of the city shall observe all safety rules applicable to the premises established by the industrial user, and the industrial user shall be held harmless for injury or death to city employees, and the city shall indemnify the industrial user against loss or damage to its property by city employees and against liability claims and damages for personal injury or property damage asserted against the industrial user and growing out of the gauging and sampling operation, except as such may be caused by negligence or failure of the industrial user to maintain safe conditions as required in this chapter.